Medical systems such as those that are implantable often utilize a medical device coupled to a medical lead. The medical lead may be fully or partially implanted within the body of the patient and the medical lead extends from the internal or external site where the medical device is located to the internal site where the electrical sensing and/or stimulation will occur. A distal end of the medical lead includes electrodes that provide the sensing and/or stimulation interface to the tissue of the patient. A proximal end of the medical lead includes electrical connectors that make physical connection with electrical contacts within a header of the medical device. Electrical conductors within the medical lead carry signals between the electrical connectors and the electrodes.
Typically, the medical lead and the medical device are separate items that are coupled together once implantation of the medical lead is completed. A clinician manually inserts the proximal end of the medical lead into the header of the medical device. The proximal end of the medical lead needs to be fully inserted into the header to ensure that each electrical connector of the medical lead makes electrical connection to a corresponding electrical contact of the header. If the medical lead is not fully inserted, one or more of the electrical connectors may not make contact with a corresponding electrical contact, and as a result, a corresponding one or more electrodes of the medical lead will not be functional.
The medical lead may also be inserted too far. For the reasons stated above regarding failing to fully insert the lead, a clinician may be overly zealous when inserting the lead and may damage the lead by continuing to apply insertion force once the lead is already fully inserted. Such lead damage may also cause one or more electrodes of the medical lead to not be functional.
Various techniques have been employed to assist the clinician in determining when a lead has been fully inserted so that insertion force can be stopped. For instance, headers of the medical devices may be transparent so that the clinician may view the lead as it passes into the header. However, medical devices and medical leads continue to be miniaturized to the point that judging the location of the lead relative to the electrical contacts within the header is difficult.
Other techniques utilize impedance measurements for the electrical pathways from the electrical contacts of the header to the electrodes. These impedance measurements provide only a gross assessment in that an electrical connector may have only a slight electrical connection to an electrical contact where that slight connection may fail over time due to small movements of the medical lead within the header, yet the impedance measurement taken immediately after insertion may indicate that adequate insertion has occurred. As another drawback, these impedance measurements involve the interface of the electrodes to the tissue and this interface may provide unreliable results particularly immediately after lead implantation when lead insertion into the medical device typically occurs.